In 1992, since Heeger of UCSB initially exhibited a possibility of a photovoltaic cell using an organic polymer, many studies thereof have been presently conducted. The cell is a heterojunction thin film diode in which an organic polymer absorbing light and a C60 fullerene derivative or a C70 fullerene derivative having very high electrophilicity are mixed with each other, and adopts ITO (indium tin oxide) that is a transparent electrode as an anode and a metal electrode having a low work function, such as Al, as a cathode material.
Light is absorbed in a photoactive layer constituted by the organic polymer to form an electron-hole pair (or exciton). There is a technology in which after the electron-hole pair moves to an interface between the copolymer and the C60 fullerene derivative or C70 fullerene derivative to be separated into electrons and holes, the electrons move to the metal electrode and the holes move to the transparent electrode, thereby generating the electrons.
Currently, efficiency of the organic polymer thin film photovoltaic cell using the organic polymer comes to 7 to 8% (Nature Photonics, 2009, 3, 649-653).
However, currently, efficiency of the organic polymer photovoltaic cell has a low level as compared to maximum efficiency (˜39%) of the photovoltaic cell using silicone. There is a demand for developing the organic photovoltaic cell having higher efficiency.